Liquid crystal display devices are thin and lightweight and have low power consumption. For these reasons, use in liquid crystal displays for laptop computers and notebooks, as well as for information display portions of personal digital assistants such as mobile phones, has become widespread.
Such conventional liquid crystal display devices are configured such that a required power supply voltage from an external power supply circuit is supplied to a driver circuit in the liquid crystal display panel. Specifically, a conventional power supply circuit, as shown in FIG. 21, is such that a reference voltage is stepped up to a high voltage by a booster circuit 140 including a transformer, this high voltage is divided by a voltage divider circuit 141 having a plurality of resisters (voltage divider resisters) connected in series, and a plurality of driving voltages V1-V3 (for example, V3=15, V2=5, V=−3) for driving the liquid crystal elements are generated from each of the points of voltage division via voltage followers 142.
In such a prior art example, there are the following problems.
1. Because the conversion efficiency of the booster circuit including the transformer is poor, the power consumption of this portion increases.
2. Because the boosted high voltages are divided by a plurality of voltage divider resistors connected in series in order to obtain the desired plurality of driving voltages, excess power consumption by the voltage divider resistors inherently arises with voltage division.
3. Because the power supply circuit is an external circuit, the reliability of the connection of the liquid crystal display panel with the driver circuit suffers.